Differential pressure actuated ballcock valves are well-known in water storage installations, especially in toilet tanks where a volume of water needed to flush a toilet or urinal is stored until it is released by opening a tank valve. The tank valve is opened by the user, usually by lifting it with a linkage of some kind. It floats for a while as the water level lowers, and then closes to permit the tank to refill.
The ballcock valve is responsive to the water level. It includes a float of some kind which causes the valve to close when the water level is suitably high, and opens when the level is lower so to provide water to refill the tank.
Early ballcock valves relied on the direct leverage force of the float, exerted through a lever arm, to hold the valve closed. The more modern valves do not require such "brute" force. Instead, the lever arm reacts with a differential pressure valve in which a pressure-responsive diaphragm acts to open or close the valve when a bias force on one side is exerted or vented The lever arm merely acts to open or close a vent port. A well-known example of such a valve is shown in applicant's U.S. Pat. No. 5,318,062, issued Jun. 7, 1994, which is incorporated herein its entirety. This invention is an improvement on this patented valve.
Ballcock valves have a long and successful history of reliability and longevity. Art is surprising that valves which are trusted to store and control very substantial volumes of water in very sensitive areas are so inexpensive. A valve which costs only a few dollars at retail will be installed in a toilet tank and forgotten about for years.
The potential for damages if one of these fails is surprisingly large. For example a leaking valve which permits overflow from the tank or the commode in an upper floor of a building can result in severe water damage to walls and contents in multiple floors below. Long-term reliability of this type of valve is a fundamental requirement.
In most fields of valves, reliability is purchased by extreme upgrading of the bulk and cost of materials and parts in the valve structure. An examination of fluid control valves in process controls and the like bear witness to this. In brief, valves used to control fluids in high risk areas are usually very expensive.
Cost in high risk applications is ordinarily acceptable, but in plumbing, and especially in housing and in the aftermarket for repair and replacement products directed to the housing market, there is not the luxury of comfortable extra cost for over-design. Instead, fractions of pennies in manufacturing cost become important, especially in mass markets of millions of valves, and more importantly in these days of low-cost labor of foreign competition. Molded plastic valves which would have tolerated manufacturing costs on the order of five dollars must now be made for less than one dollar and must be fully competitive, reliable, and long-lived.
The cost of any product, and especially of one which is made as an assembly of many parts, includes not only the parts themselves, but the cost of assembling them. To this must be added the cost of rejects and reworks when the basic design is insufficiently reliable to assure that the parts will be assembled not only quickly but correctly, and that when they are assembled the valve will work.
Accordingly, it is not the object of this invention to improve the function of the valve. Working valves for toilet tanks have been successfully supplied for many decades. Instead it is the object of this invention to provide valves for the same purpose with an elegantly simple construction that can be manufactured very economically, and which can quickly and reliably be assembled by well-paid labor, still producing a product which competes economically and functionally with the best-known products produced in low cost countries.
The major improvements in these valves were made long ago. Now there remains the objective of producing them at the very least cost. It is here that ballcock inventions will result in reduced prices, and the ability to produce lowest-cost products using relatively high cost labor. Both of these criteria are favored by the instant invention.